Production of alkenyl aromatic compounds



PatentedNov. 11, 1947 UNITED STATES- PATENT orrics PRODUCTION OF ALKENYL AROMATIC v COMPOUNDS William N. Axe, Bartlesville, kla., assignorio Phillips Petroleum Company, a corporation of Delaware No Drawing. Application August 28, 1944, Serial No. 551,621

, may be used for the production of normal aliphatic derivatives of such compounds as aminobenzenes, aminonaphthalenes, phenols, naphthols, aminophenols, aminonaphthols, quinolines, and the like. These materials can be used in the preparation of oxidation inhibitors, pharmaceuticals, dyestufis, and explosives. The development of the full potentialities of normal aliphatic derivatives of such compounds has been precluded by the absence of suitable sources of such compounds. Thus, when olefins are used to alkylate aromatic compounds the normal alkyl derivative is produced only in the case of ethylene and with other olefins it is impossible to produce a normal alkylderivative by catalytic alkylation.

" Synthetic methods for the production of normal alkyl derivatives have been limited heretofore to reactions of the Wurtz-Fittig type in which aromatic halides have been condensed, in the presence of a metal such as sodium, with normal alkyl halides. The best yields reported for such reactions have not exceeded about 30 per cent of the theoretical yield and more often actual yields are from about to per cent of the theoretical yields. Other disadvantages of. such synthesis operations include the use of large quantities of metals such as sodium with app ec ble a tend ant hazards, the employment of expensive intermediate compounds, the necessity for special solvents, and the relatively difiicult production of normal alkyl halides.

An object of this invention is to produce normal aliphatic derivatives of aromatic compounds.

Another object of this invention is to produce normal alkyl derivatives of aromatic compounds.

Still another object of this invention is to produce normal butyl benzene;

Further objects and advantages of my invention will become apparent to one skilled in the art from the accompanying disclosure and discussion.

I have now found that aromatic compounds, including aromatic hydrocarbons, phenols, naphthols, and aromatic halides, can be reacted with normal 1,3-diolefins to produce alkenyl derivatives of said aromatic compounds. I have further found that such alkenyl derivatives include normal monoalkenyl derivatives which can be successfully subjected to nondestructive hydrogenation to produce the corresponding normal alkyl derivatives. I have further discovered that such derivatives can be produced in extremely high yieldsand can be recovered in substantial quantities in a condition'of high purity. As the aromatic reactant of my process I prefer to use benzene, naphthalene, simple alkyl derivatives of these hydrocarbons such as toluene, ethylben-v zene, xylenes, and the like, phenol, naphthols,

and simple alkyl derivatives of these materials, and aromatic halides such as phenyl chloride, phenyl bromide, one of thenaphthyl chlorides, and the like, although other alkenylatable aromatic compounds are not to be excludedfrom the broad concept of my invention. As the diolefin. reactant 'I prefer to use a low-boiling normal 1,3- diolefin such as 1,3-butadlene, 1,3-pentadiene, 1,3-hexadiene, and the like. ,Although it is a primary object of my invention to produce normal aliphatic derivatives by the use of normal 1,3-diolefins, it is to be understood that alkyl derivatives of normal 1,3-diolefins, suchas 5-methyl-l,3-hexadiene and 6-methyl-l,3-heptadiene, to produce aromatic derivatives such as 1-phenyl-5- methyl hexylene and 1-pheny1-6-methy1 heptylene, and the like, are not to be excluded from the broad concepts of my invention.

Broad features of this process may be more readily understood by considering a typicalprocedure. A blend of butadiene in benzene, in which the benzene is present in substantial molar excess, serves as the primary feed stock. The blend is charged to a reaction zone at moderate temperatures and pressures where it is intimately commingled with a liquid complex compound of boron fluoride such as those to be hereinafter described. The eilluent is preferably continuously removed from the reaction zone and after mechanical separation of the catalyst phase, the hydrocarbon stream is washed free of dissolved boron fluoride and the excess benzene is recovered by fractional distillation. The debenzenized product is further fractionally distilled to separate a main product (normal butenyl benzene, or phenyl butene) boiling at about 365 to about 370 F., and a higher-boiling kettle product. main product fraction may be hydrogenated over a conventional hydrogenation catalyst such as Raney' nickel, platinum or any of the more rug- The.

constant.

ged industrial hydrogenation catalysts to yield nbutylbenzene; which ordinarily requires no further purification.

I have found that eflicient catalysts for such alkenylation reactions can be prepared by subit may be used in admixture with porous granular catalyst supports such as activated charcoal,

stantially saturating an alcohol, preferably a monohydric aliphatic alcohol, with a boron trihalide. A preferred trihalide is boron triiiuoride, although I do not intend to exclude other boron trihalides, particularly boron trichloride and boron tribromide which are low-boiling materials. Preferably the alcohol is one containing not more than about six carbon -atoms,per molecule and advantageous results are obtained when the catapressure until absorption of the boron trihalide is complete. With alcohols containing four or more carbon atoms per molecule, and more especially with secondary and/r tertiary alcohols, side reactions may take place to produce oily polymers which are believed to be olefin polymers. Such-polymers may be removed in any suitable manner, as by layer separation and/or distillation orthe like. Although such side reactions reduce the yield of catalyst somewhat, compounds of excellent and specific catalytic activity are obtained from such alcohols. During the course of preparing the'catalyst an exothermic reaction appears to take place, and it is generally desirable tocool this reacting mixture to prevent excessive' temperature rise. The catalyst is preferably prepared at a temperature not greater than about-i150" and generally a temperature between {about 75 and 95 F. produces improved results. Completion of the catalyst-forming reaction is indicated by a cessation of heat development and also by the presence of free boron trihalide. This catalyst preparation may be conducted, if desired, under pressure, particularly when using boron trifluoride or boron trichloride. As was indicated in the aforesaid copending application, in most instances the reaction is com- I pleted with the absorption of one mol of boron fluoride per mol of alcohol. For example, in the preparation of a sec-butyl alcohol-boron fluoride catalyst one mol of alcohol absorbs approximately one mol of boron fluoride. Similarly, an isopropyl alcohol-boron fluoride catalyst was prepared by saturating isopropyl alcohol cooled in an ice bath with anhydrous boron fluoride. .At

activated alumina, activated bauxite, and the like, although when using boron trifluoride-containing complexes it is preferable not to use a granular material containing appreciable amounts of silica. v

In the alkenylation step the reaction appears to be primarily monoalkenylation to form monoalkenyl derivatives of the aromatic compound.

It also appears that secondary reactions take place to certain extents, including cyclization and/or polymerization of the resulting monoalkenyl derivatives. the observation that the aromatic compound reacted is molecularly equivalent to the'diolefln reacted. If extensive polyalkenylation occurred, to form dior tri-alkenyl aromatic derivatives, the amount of aromatic hydrocarbon reacted would be substantially less than the molecular equivalent of the diolefin, while if the monoalkenyl derlvative entered'into reaction with the aromatic conditions of operation, a conclusion deduced from.

the end of the catalyst preparation reaction, es-

sentially one mol of boron fluoride had been absorbed per mol of alcohol. When the catalyst is subsequently used in the alkenylation reaction it tends to lose appreciable quantities of the boron trihalide during use, this loss being accompanied by a decreasein' activity. For this reason it is desirable to add, during a continuous process, small amounts of the boron trihalide initially used to prepare the catalyst, continuously or intermittently, in order that the activity of the catalyst willremain or be maintained substantial'y In most instances the resulting active catalytic material is a liquid and can be readily employed as such, preferably with inti mate mixing with the reaction mixture. If it i desired to use such a catalyst in the 89nd form with the same reactants.

hydrocarbon, to form th corresponding di-substituted paraflin hydrocarbon, the amount of arcmatic hydrocarbon reacted would be substantially greater than a molecular equivalent of the diolefin. No appreciable polymerization of the diolefin is believed to take place under preferred a consideration of the relative amounts of reactants which undergo reaction and from the characteristics of such high-boiling products. Such results contrast with the results obtained when catalysts such as sulfuric acid are used Thus, when benzene and LE-butadiene are reacted in the presence of sulfuric acid it has been reported that the product is diphenylbutane and that no phenylbutene is produced.

In order to favor the desired primary reaction I prefer to use moderate reaction temperatures, relatively short reaction periods, and relatively high molar ratios of aromatic compound to di olefin reactant. The reaction may be satisfactorily and conveniently conducted at a temperature between about and about 150 F., with a temperature between about to and about to F. being preferred. Temperatures above F., or below 75? F., are not to be excluded, however. The average reaction time may be between a few minutes and a few hours, with satisfactory results being obtained with a reaction time between about 5 and about 20 minutes. The molar ratio of aromatic compounds to diolefln in the feed to a continuous reaction step may be between about 2:1 and about 10:1 with satisfactory operation generally being obtained previously stated, it is preferred that the reacting I mixture and the catalyst be intimately admixed. This maybe accomplished by efilcient stirring mechanism, by continuously recirculating in a closed cycle a substantial amount of the reaction mixture comprising reactants, products and catalyst, by pumping such a reaction mixture This conclusion is based on through a long tube coil at a rate such that conditions of turbulent now exist, or by other means well known to those skilled in the art of hydrocarbon alkylatlons. It is preferred that the reaction mixture contain at least about 5 per cent by volume of the catalyst and that the amount of catalyst present should notexceed that which will permit a continuous phase of reacting ma terials when the reaction mixture is intimately admixed. Thus it is desired that the catalyst phase not be the continuous phase when a liquid catalyst is used. Inert materials may be present during the reaction, such as relatively nonreactive impurities normally accompanying the reactants, added low-boiling paraflin hydrocarbons such as a parafilnic naphtha fraction, or the like.

When 1,3-butadiene is the diolefin reactant the monoalkenyl product is substantially completely the normal alkenyl derivative. With diolefin reactants containing a higher number of carbon atoms per molecule such high yields of the normal derivative will often not be obtained but it will still be possible to obtain quit'e substantial yields of the normal alkenyl derivative. In any case a fraction containing, or comprising essentially, the desired normal alkenyl derivative may .be readily separated from the reaction eilluents,

generally by passing the eiiiuents to a settling chamber wherein the catalyst separates from a tion of any desired purity.

As will be appreciated the normal alkenyl derivative may, in many instances, be a desired tures ranging from about 75 F. to about 150 F.

Example I To a mechanically agitated emulsion of ml. oi CHsOHBFa catalyst in 150 ml. of benzene, at atmospheric pressure, gaseous butadiene was added at a rate of 5.1 gaseous liters per hour until 49.2 g. of the diolefin had been charged. The temperature of the reaction mixture was maintained at IE-85 F. The hydrocarbon was separated mechanically from the catalyst phase and the product layer was washed and dried. The

product phase was then fractionally distilled at atmospheric pressure to yield a butenylbenzene cut boiling at 366--369 F. which amounted to 52 weight per cent of the total debenzenized product.

The amount of unreacted benzene recovered in-' dicated that 71.4 g. of benzene was consumed while the required amount of benzene for equimolecular union with butadiene was calculated hydrocarbons are reacted in accordance with my invention, not only may normal alkyl derivatives thereof be produced by such a nondestructive hydrogenation, but the hydrogenation may be extended to include partial or complete saturation of the aromatic to react a benzene with a low-boiling 1,3-diolefin to produce a normal alkenyl derivative of said benzene, and subsequently to hydrogenate this" product, in one or more steps, to produce a normal alkyl derivative or a corresponding normal alkyl cyclohexane. Likewise, a naphthalene may be converted to a normal alkenyl derivative, and

this product may subsequently be hydrogenated, in one or more steps, to produce a normal alkyl derivative, a normal alkyl tetralin, or a normal alkyl decalin. For such hydrogenations any suitable known nondestructive hydrogenation catalyst may be employed which is capable of effecting saturation of the alkenyl group without saturation of the aromatic nucleus or without reaction pound. So-called-Raney nickel" has been found desirable in accomplishing this result when the hydrogenation is conducted at moderate temperatures and pressures. More drastic hydrogenation conditions will be necessary in order to produce the more saturated products cussed.

Thus, in the selective hydrogenation of the olefinic linkage, the rate of absorption of hydrogen may amount to about 1 mol per hour at pressures of to 50 pounds per square inch andtemperajust disliquid phase contaimng unreacted charge stock and reaction products, and separating from this liquid phase, as by fractional distillation, a fracto be 71.0 g.

Reduction of the butenylbenzene fraction was carried out as a batch operation under a hydrogen pressure of 15-50 p. s. i. g. and in .the presence of Raney nickel catalyst. The saturated n-butylbenzene was identified by its boiling range of 359 360 and by its refractive index, N 1.4889.

Example II Operating under conditions similar to those given inExample I, toluene may be reacted with '(l,3-pentadiene) to produce n-penpiperylene tenyltoluene. In this instance, the toluene-free product is subjected toa preliminary fractionation under 10 mm. pressure to efiect a rough separation of higher-boiling products from the nucleus. Thus it is possible pentenyltoluene.

' alkenylate.

} Final purification involves fractional distillation at atmospheric pressure to give a product boiling at about 430-440 F; amounting to about per cent of the total Analytical data and oxidation reactions indicate this material to be essentially 1 -j(p-tolyl)-2-pentene. Nondestructive geriation results in quantitative reduction to l-methyl-4-n-pentylbenzene having substantially the same boiling range as the original alkenyl derivative.

" Although I have described my invention in considerable detail, with the inclusion of certain specific embodiments, it is not intended that the scope of the invention be limited unduly by such details.

I claim: 1. A process for the production of normal alkenyl aromatic hydrocarbons, which comprises of any other negative group in the alkenyl comreacting an aromatic hydrocarbon with anormal 1,3-diolefin ata reaction temperature between aliphatic alcohol and a boron trihalide and resulting from saturating a monohydric aliphatic alcohol with a boron trihalide, and maintaining hydro- -matic hydrocarbons, which comprises reacting an F. in the presence of a catalyst complex consisting of substantially one molof boron trifluoride per mol of an alcohol.

4. A process for the production of phenyl bumaterial comprising phenyl butene from efliuents of 5. A process for the production of an aliphatic derivative of an prises reacting an alkenylatable aromatic-compound with an open chain 1,3-diolefin in the presence of a complex catalyst consisting of substantially one mol of a boron trihalide per mol of an alcohol.

6., 'A process for the alkenylation of an aromatic hydrocarbon, which comprises reacting a lowa monohydric aliphatic alcohol aving not more than six carbon atoms per molecule.

v7. A process for the alkenylation of an aromatic hydrocarbon, which comprises reacting 1,3-pentadiene with a molar excess of an alkenylatable aromatic hydrocarbon under alkenylationconditions in the presence of a catalyst complex consisting of substantially one mol of boron trifi-uoride per F. in the presence of a catalyst molecule.

8 mol of a monohydricaliphatic alcohol having not more than six carbon atoms per molecule.

8. A process for the alkenylation of an aromatic hydrocarbon, whickmprises reacting l,3'-butadiene with amolar under alkenylation condi- I tions in the presence of a catalyst complex con-- sisting of substantially one mol of boron trifiuoride per mol of a monohydric aliphatic alcohol having not more than six carbon atoms per .9. A process for the production of an aliphatic derivative of an aromatic compound, which comprises reacting an alkenylatable aromatic compoundwith an open. chain 1,3-diolefin in the presence of a complex catalyst not greater than about.

10. A process which comprises reacting an alkenylatable aromatic hydrocarbon with an open chain 1,3-diolefin at a reaction temperature such major portion of the resulting reaction products is an alkenyl derivative of said aromatic compound and reaction products comprising poly mers of said alkenyl derivative, polymers of said WILLIAM N. AXE.

REFERENCES CITED The following references are of me of this patent:

UNITED STATES PATENTS Number Name 1 Date 2,290,211 Schaad July 21, 1942 2,382,260 Schaad Aug. 14, 1945 v FOREIGN PATENTS Number Country Date 799,016 France Mar. 23, 1936 OTHER REFERENCES Beilstein, 2nd Supp, page 378. (Division 6.) Muskat et al., Chem. Abs., vol. 25, 3972 (1931). (Pat. Off. Lib.) I

record in the 

